For example, there has been known a die cushion controller disclosed in Patent Document 1, which controls an ascending/descending movement of a die cushion pad driven by an electric servomotor. In the die cushion controller of Patent Document 1, a load (a pressure) generated in a die cushion pad (hereinafter, this pressure will be referred to as a “cushion pressure”) is obtained based on an electric current value of the electric servomotor, and the electric servomotor is controlled such that the obtained cushion pressure follows a pressure pattern of a preset cushion pressure.
In this regard, the pressure pattern as disclosed in Patent Document 1 is in a form of a free-form curve where the cushion pressure starts to gently increase at a time point at which an upper die contacts with a workpiece to reach a maximum target pressure and then gently decreases.
[Patent Document] JP-A-10-202327